Nowadays there is an increasing need in the fields of vegetable and mushroom production and sales for bioproducts containing no residues of chemical pesticides. Among the effective chemical pesticides only the inorganic copper-compositions are allowed in the course of production of bioproducts. The number of copper resistant mutants among the vegetable pathogen microorganisms has increased a lot in the last couple of years, thus these copper containing agents alone are insufficient to achieve effective and reliable pest control. One possible solution to overcome this problem is to effect an integrated pest control using copper containing agents and biocontrol compositions. Biocontrol products may also be used alone, but in such cases the highest efficiency of the best compositions is still under 50 percent. The majority of the antibacterial or antifungal biocontrol products presently available in the world market contain one component as active agent, which is a bacterium or fungi possessing antagonist and/or parasite features.
The bacterial maculation may affect every produced mushroom species in the field of mushroom production, strains less susceptible (or even resistant) to the pathogen are not known to date. The bacterial maculation infects very quickly in the mushroom production premises because on one hand the Pseudomonas strains are very aggressive pathogens through their toxins and on the other hand the conditions of the mushroom production are ideal for them. The loss of the yield often reaches even 50 to 60 percent. The damage caused by this bacterial pathogen represents as much as 800 million HUF loss in revenues per annum considering an average of 25 000 tons of the cultivated mushroom per year. The situation is made even worse by the fact that there is no registered pest controlling agent in the mushroom production.
Certain strains of the Pseudomonas genus, among them especially Pseudomonas fluorescens strains have long been used for biocontrol purposes. There are marketed compositions which are effective mainly against plant pathogen fungi. Their effectiveness is first of all explained by different antibiotics secreted to the extra-cellular space, which antagonize mainly fungi: phenazine derivatives, 2,4-diacetylfloroglucinol, and pyrrolnitrin. Pseudomonas fluorescens strains are also successfully used against bacteria for biocontrol. E.g. a Pseudomonas species producing 2,4-diacetylfloroglucinol (DAPG) was used against Erwinia causing bacterial soft rot in potato. In the presence of the DAPG producing Pseudomonas the plant was not infected. The results show that DAPG is a significant biocontrol against determinant bacteria as well. The antibiotics secreted by bacteria are capable of inhibiting the life functions of other microorganisms already at low concentration, and even causing their death. In cases of a number of plants it is proven that the antibiotics production of the bacteria suppressed the plant pathogen and the disease caused by it. It has been demonstrated that these effects are present not only in laboratory circumstances, but also in a natural environment, in the soil. To perform an effective biocontrol, the species used must produce sufficient amount of the antibiotics in the proximity of the pathogen. The particular amount needed is highly varied and is different in cases of the different pathogens. In case of a number of Pseudomonas strains used in biocontrol the multiplied antibiotics production is known. The effectiveness of P. fluorescens is further increased by the excellent competition capability of the strains. In the competition among the Pseudomonas fluorescens strains the competition with siderophores (iron-binding organic compounds) for the free iron-ions has high importance as well. The biocontrol based on competition has successfully been used against e.g. Agrobacterium radiobacter, A. tumefaciens, or the pathogen Fusarium oxysporum, F. oxysporum strains.